<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function fn(resolve){
            console.log(123);
            resolve('ok');
        }
        fn(fn2)

        function fn2(val){
            console.log(val);
            console.log('fn2打印');
        }

        
    </script>
</body>
</html>